1. Field of the Invention
The present invention relates to catheter distal protection devices, and specifically to filter and occluder mechanisms for use during intravascular procedures to capture embolic particles.
2. Background of the Invention
Diseased blood vessels are a widespread medical condition. For example, a narrowing, or stenosis may form by local thickening of the vessel walls, or a lesion may form by an accumulation of atherosclerotic plaque on blood vessel walls. A thrombus (blood clot) may also form in a vessel, especially in a region of turbulent flow adjacent a narrowing. Blood vessel walls may also become thin and weak, possibly leading to the formation of an aneurysm. If a blood vessel becomes weakened or narrowed, clinical intervention may be required to prevent rupture or complete occlusion of the vessels. While many different surgical procedures are associated with the treatment of vascular diseases, the use of catheters is generally preferred due to the minimally invasive nature of interventional catheterization.
Many types of procedures involve the use of catheters to treat stenotic vessels or thromboses. One type of procedure is percutaneous transluminal coronary angioplasty, or PTCA, which involves the inflation of a balloon within a stenosis to expand a coronary blood vessel. Additionally, a stent may be implanted in conjunction with PTCA to support the dilated artery. Various other procedures are also common, such as a thrombectomy to remove a thrombus or a portion thereof, or an atherectomy to cut or abrade a stenosis within a diseased portion of the vessel.
Each of these intravascular procedures is associated with a common risk: that an embolic particle may be dislodged during the procedure and migrate through the circulatory system, possibly causing ischaemia, infarctions or strokes. To prevent damage caused by such loosened debris, practitioners may attempt to capture the embolic particles using temporary distal protection devices such as occluder catheters or filter guidewires. Particles that are trapped or collected by such devices may be aspirated from the body lumen, chemically lysed in situ, or removed with the distal protection device at the end of the procedure.
Known distal protection devices have relative advantages and drawbacks. Occlusion devices can prevent all of the embolic debris from migrating such that the stopped debris may then be removed by an aspiration mechanism. However, the duration of use of an occluder is limited because an occluder also blocks blood flow. Therefore, occlusion is not appropriate in all cases. Further, aspirating the stopped embolic particles can be an imperfect process, and some embolic particles may escape when the occluder is collapsed for withdrawal.
Embolic filters also suffer from some drawbacks. Embolic filters may be used for longer duration than occluders because filtering devices do not prevent the flow of fluid. However, embolic filters may be limited in their ability to remove very small embolic particles from the bloodstream. Further, embolic filters may become full of embolic debris and occlude the vessel unless they are emptied by aspiration or removed from the patient's vessel.
Therefore, a need exists in the art to obtain the benefits associated with occluders, such as complete particle capture, while also being able to re-capture particles that may be lost during the collapse of an occluder if aspiration was imperfect. An embolic filter and occluder combination may fill such a need.
A combination of filters and occluders on the same catheter has been proposed for use in heart surgery where the heart must be arrested and isolated from the rest of the cardiovascular system. For example, U.S. Pat. No. 6,090,097 to Barbut et al., the entirety of which is incorporated herein by reference thereto, discloses a balloon arterial cannula that includes a balloon occluder and a blood filtration assembly. However, in this device, the filter and occluder are spatially separated along the shaft of the cannula. Such a separation distance is not practical for use in, for example, an angioplasty procedure.
Further, medical balloons are often used to deploy implantable filters, such as vena cava filters. Such a filter is described in U.S. Pat. No. 4,793,348 to Palmaz, the entirety of which is incorporated herein by reference thereto. This type of filter is detached from the catheter and is permanently implanted to provide prophylaxis in case a blood clot moves into the major veins. Also, balloons used for the deployment of this type of filter are not intended to occlude the vessel for the capture of embolic particles.
Therefore, a need exists in the art for an embolic filter-occluder combination for use as a distal protection device during the treatment of diseased vessels.